The activity of soluble malate dehydrogenase (E. C. 1.1.1.37, sMdh) in mouse hepatoma BW7756 is reduced in comparison with C57L/J host liver and normal C57/L liver enzyme. In addition, the sMdh in normal liver consists of 4 molecular components separable by starch gel electrophoresis. Only the main isozyme form is present in the hepatoma and fetal liver. This project is directed towards understanding the molecular relationships of the soluble forms, studying the rates of synthesis and degradation of the soluble enzyme in liver and hepatoma, and to determine the developmental expression of the enzyme. Other enzymes are also being studied in liver and hepatoma that are at other metabolic points which show altered activity or isozyme pattern in hepatoma when compared to liver tissue.